Method of producing light-conducting LED bodies of a material that is free-flowing before final solidification, by introduction into a mold, where the individual LED body comprises at least one light-emitting chip and at least two electrodes—connected electrically with the chip—and where the free-flowing material is injected between a floor region of the mold and the chip, at least approximately parallel to the chip plane and at least approximately normal to a plane formed by two electrodes, between the electrodes.
DE 101 59 522 discloses a method of this kind for producing light-emitting diodes. The diode to be produced is a radial LED, whose mold is filled by radial injection of free-flowing material. The material is injected under the chip normal to a plane established by the electrodes. In this method, the material filling the mold flows from below around the chip and the bonding wire placed over it. By this method the bonding wire is protected from being torn off by the incoming material. However, it frequently happens that—viewed in the direction of injection of material—the material introduced into the mold piles up on one side before or after the electrodes. As a result, the flow front flowing predominantly toward one side of the chip can push the bonding wire aside hard enough to cause it to come into contact with the cathode. As further flow toward the diode takes place, the component fails due to short circuit.
The present invention therefore is based on the problem of developing a method of producing light-conducting LED bodies in which, at customary output capacities of known injection or molding operations, the LED electronics are not adversely affected.
This problem is solved by the features of the main claim. For this purpose, the volumetric flow of a free-flowing material, at a distance of the electrode plane from the charging point that is greater than 30% of the distance between the charging point and the mold side of the mold lying opposite the charging point—is choked above the charging point and below the chip plane on the mold side of the charging point by at least one cross-sectional constriction, while—at a distance that is smaller than or equal to 30% of this distance—choking takes place on the mold side lying opposite the charging point.
By this method of producing a luminescent diode, a given specification of the charging point and of the direction of introduction in conjunction with a prescribed choking of the volumetric flow of material at a defined spot procures a flow condition that permits controlled, uniform filling of the mold without any damage to the LED electronics. For choking, a molding element that narrows the cross section of flow between the front edge of the molding element and the chip is located in the individual mold cavity opposite the electrode fence. The geometric dimension of the molding element and its surface structure turned toward the volumetric flow is selected according to the type of synthetic material, or as necessary. This is simple to accomplish with the use of replaceable choke slides bearing the molding element.
The molding element causes the in-flowing material to be choked at least on one side in such a way that the flow fronts moving from below against the chip on both sides of the electrodes contact and flow around the chip and the bonding wire virtually simultaneously. The virtually simultaneous envelopment of the bonding wire stabilizes the bonding wire in its structurally preplanned position.
The method is likewise applicable to luminescent diodes having a plurality of chips and electrodes.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.